- Ethylenediamine promoted the hydrogenative coupling of nitroarenes over Ni/C catalyst
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Azobenzene and its derivatives are key raw materials and it is an environmentally friendly method for the preparation of azobenzene by hydrogenative coupling of nitrobenzene. The development of nickel based catalyst for organic transformations is of importance because of its relatively low cost and toxicity. In this work, we found that ethylenediamine can enrich the electron state of Ni and make the azobenzene easily desorb from the surface of the catalyst, which inhibits the hydrogenation of azobenzene to aniline. The selectivity of azobenzene is greatly improved. When the ratio of Ni and ethylenediamine is 1:10, the yield of the azobenzene can reach 95.5%.
- Yang, Youdi,Li, Shaopeng,Xie, Chao,Liu, Hangyu,Wang, Yanyan,Mei, Qingqing,Liu, Huizhen,Han, Buxing
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- Catalytic nickel nanoparticles embedded in a mesoporous metal-organic framework
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Ni nanoparticles embedded in the pores of a mesoporous MOF (MesMOF-1) act as a catalyst for hydrogenolysis of nitrobenzene or hydrogenation of styrene. The Royal Society of Chemistry 2010.
- Park, Young Kwan,Choi, Sang Beom,Nam, Hye Jin,Jung, Duk-Young,Ahn, Hee Choon,Choi, Kihang,Furukawa, Hiroyasu,Kim, Jaheon
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- Silver and palladium alloy nanoparticle catalysts: Reductive coupling of nitrobenzene through light irradiation
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Silver-palladium (Ag-Pd) alloy nanoparticles strongly absorb visible light and exhibit significantly higher photocatalytic activity compared to both pure palladium (Pd) and silver (Ag) nanoparticles. Photocatalysts of Ag-Pd alloy nanoparticles on ZrO2 and Al2O3 supports are developed to catalyze the nitroaromatic coupling to the corresponding azo compounds under visible light irradiation. Ag-Pd alloy NP/ZrO2 exhibited the highest photocatalytic activity for nitrobenzene coupling to azobenzene (yield of ~80% in 3 hours). The photocatalytic efficiency could be optimized by altering the Ag:Pd ratio of the alloy nanoparticles, irradiation light intensity, temperature and wavelength. The rate of the reaction depends on the population and energy of the excited electrons, which can be improved by increasing the light intensity or by using a shorter wavelength. The knowledge developed in this study may inspire further studies on Ag alloy photocatalysts and organic syntheses using Ag-Pd nanoparticle catalysts driven under visible light Irradiation.
- Peiris, Sunari,Sarina, Sarina,Han, Chenhui,Xiao, Qi,Zhu, Huai-Yong
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- A NOVEL REACTION OF ACETANILIDE WITH NITROBENZENE IN DMSO - AN UNUSUAL SOLVENT ASSISTED REGIOSELECTIVE AROMATIC NUCLEOPHILIC SUBSTITUTION
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The reaction of acetanilide (1) with nitrobenzene (2) in the presence of a base in DMSO yielded p-nitrosodiphenylamine (3) as the major product.This unusual regioselective formation of the deoxygenated product 3 has been rationalized in terms of solvent effects exerted by DMSO.
- Ayyangar, N. R.,Naik, S. N.,Srinivasan, K. V.
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- Synthesis of azo compounds by nanosized iron-promoted reductive coupling of aromatic nitro compounds
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Treatment of a variety of aromatic nitro compounds with the active-iron based reducing system composed of FeCl2·4H2O, an excess of lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol %) in THF at room temperature, led to the formation of the corresponding symmetrically substituted azo compounds in good yield, resulting from a reductive coupling process. Some other functionalities including carbonyl, halogen, amino and hydroxyl groups, demonstrated to be compatible with the reaction conditions, giving none reduced or coupled by-products. In all cases, the azo compounds formed have not experienced over-reduction to the corresponding hydrazo or amino derivatives even upon prolonged heating or using an excess of the reducing system.
- Moglie, Yanina,Vitale, Cristian,Radivoy, Gabriel
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- A new preparative method, characterization, and reactivity of disulphide dication salts of cyclic bis-sulphides: R2S-SR2· 2CF3SO3-
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The reaction of 1,5-dithiacyclo-octane 1-oxide with trifluoromethanesulphonic anhydride affords the corresponding disulphide dication as a stable crystalline salt which serves as an oxidizing agent in the oxidation of 1,2-diphenylhydrazine; the disulphide dication of 1,4-dithiane has also been isolated.
- Fujihara, Hisashi,Akaishi, Ryouichi,Furukawa, Naomichi
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- Synthesis, Structure, and Oxidative Reactivity of a Class of Thiolate-Bridged Dichromium Complexes Featuring Antiferromagnetic Coupling Interactions
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Several thiolate-bridged dichromium complexes with Cp* (Cp=η5-C5Me5) as auxiliary ligands were designed and synthesized through the salt metathesis, which all contain two six-coordinate chromium centers in the formal valence of +3. These complexes are all paramagnetic species, which are in good agreement with the experimental results that broad and paramagnetically shifted proton resonances appear in the 1H NMR spectra. Furthermore, variable-temperature solid-state magnetic susceptibility studies reveal the two chromium centers of these complexes are both in an S=3/2 high-spin state with a strong antiferromagnetic coupling. Simulated values of antiferromagnetic coupling constant for these complexes are directly related to the distances of the two CrIII centers confirmed by X-ray crystallography. In addition, in the presence of dehalogenation agent AgPF6, complexes [Cp*CrCl(μ-SR)2CrClCp*] (3, R=Et; 4, R=iPr) and [Cp*Cr(μ-Cl)(μ-SEt)2CrCp*][BPh4] (5) containing easily removable chloride can achieve the catalytic oxidation of organic substrates, such as PPh3, 1,4-cyclohexadiene and 1,2-diphenylhydrazine under an oxygen atmosphere.
- Wei, Nianmin,Yang, Dawei,Zhang, Yixin,Wang, Baomin,Qu, Jingping
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- A new catalytic method for the selective oxidation of aniline to nitrosobenzene over titanium silicate molecular sieves, TS-1, using H2O2 as oxidant
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The oxidation of aniline to nitrosobenzene with a selectivity > 73% has been achieved using titanium silicate molecular sieves, TS-1 as catalyst and aqueous H2O2 as oxidant at 273 K in a batch reaction.
- Selvam,Ramaswamy
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- Di- and Trinuclear Iridium(III) Complexes with Poly-Mesoionic Carbenes Synthesized through Selective Base-Dependent Metalation
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Mutidentate carbene ligands based on a rigid aromatic platform are valuable synthons for generating carbene complexes with higher nuclearity. We present here the selective, base-dependent synthesis of a dinuclear or a trinuclear IrIII complex from the 1,3,5-substituted benzene derived tris-triazolium salt. The dinuclear IrIII complex features an unreacted triazolium unit which enables us to compare the metric parameters between the bonded 1,2,3-triazol-5-ylidene to their parent triazolium salt present in the same molecule. Single crystal X-ray diffraction studies confirm the di- and trinuclear nature of the complexes and establish their configuration and conformation. Both the di- and trinuclear IrIII complexes have been used for catalytic transfer hydrogenation, and these complexes are potent precatalysts delivering good to excellent yields for the reduction of benzaldehyde, acetophenone, benzophenone, and cyclohexanone. Furthermore, they show a preference for reducing nitrobenzene to either azoxybenzene or azobenzene. Mercury poisoning tests conclusively prove the homogeneous nature of the reported catalysis. The lack of orthometalation in these complexes and the possible effect thereof on catalysis are discussed. (Chemical Equation Presented).
- Maity, Ramananda,Van Der Meer, Margarethe,Hohloch, Stephan,Sarkar, Biprajit
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- Biogenic Synthesis of Gold Nanoparticles on a Green Support as a Reusable Catalyst for the Hydrogenation of Nitroarene and Quinoline
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Direct attachment of gold nanoparticles to a green support without the use of an external reducing agent and using it for removing toxic pollutants from wastewater, i. e., reduction of nitroarene to amine, are described. A novel approach involving the reduction of gold by the jute plant (Corchorus genus) stem-based (JPS) support itself to form nanoparticles (AuNPs) to be used as a catalytic system (‘dip-catalyst’) and its catalytic activity for the hydrogenation of series of nitroarenes in aqueous media are presented. AuNPs/JPS catalyst was characterized using SEM, UV-Vis, FTIR, TEM, XPS, and ICP-OES. Confined area elemental mapping exhibits uniform and homogeneous distribution of AuNPs on the support surface. TEM shows multi-faceted AuNPs in the range of 20–30 nm. The reactivity of AuNPs/JPS for the transfer hydrogenation of nitroarene as well as hydrogenation of quinoline under molecular H2 pressure was evaluated. Sodium borohydride, when used as the hydrogen source, demonstrates a high catalytic efficiency in the transfer hydrogenation reduction of 4-nitrophenol (4-NP). Quinoline is quantitatively and chemoselectively hydrogenated to 1,2,3,4-tetrahydroquinoline (py-THQ) using molecular hydrogen. Reusability studies show that AuNPs are stable on the support surface and their selectivity is not affected.
- Adeyeye Nafiu, Sodiq,Aziz, Abdul,Shaheen Shah, Syed,Shaikh, M. Nasiruzzaman
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- 1D coordination polymer based on copper(II)-containing tetrameric 1,2,3-triazole ligand from click chemistry: Magnetic and catalytic properties
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A novel tetrameric tetra[O-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)]-pentaerythritol (TBTP) has been synthesized using click chemistry strategy. TBTP was characterized and used as ligand to form new Cu(II) complexes, forming 1-D coordination polymers. Two square planar complexes were characterized by single-crystal X-ray diffraction, presenting formula [Cu(TBTP)][Cu(NO3)4] (1) and [Cu(TBTP)](NO3)2 (2). In both structures, a cationic 1-D coordination polymer (CP) has been formed. The CP contain a 1:1 Cu(II)/TBTP ratio with four neutral triazole groups coordinating the Cu(II) center, forming a Cu[sbnd]N bonds ranging 1.988(2)–2.001(2) ?. The study of the magnetic properties of compounds 1 and 2 pointed to an antiferromagnetic behavior for both compounds, defined by inter- and intra-chain dipolar interactions among their metallic centers. In addition, the complex 1 was found to be an efficient catalyst for selective oxidation of aniline to azobenzene under mild reaction conditions.
- Moraes, Leonardo C.,de Souza, Gilmar P.,Fajardo, Humberto V.,Luz, Sulusmon C.,álvarez, Eleuterio,Lloret, Francesc,Ribeiro-Viana, Renato M.,Rojo, Javier,Stumpf, Humberto O.,Figueiredo, Rute C.,Corrêa, Rodrigo S.
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- Room temperature selective reduction of nitroarenes to azoxy compounds over Ni-TiO2 catalyst
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Surface tuned Ni-TiO2 catalyst was prepared by hydro-solvothermal method using poly(diallyldimethylammonium chloride) (or PDADMAC) as a surfactant and hydrazine hydrate as a capping agent. Activity of catalyst was investigated for selective reduction of nitrobenzene to azoxybenzene in aqueous medium at room temperature, using hydrazine hydrate as the reducing agent for catalysis. It was observed that the catalyst prepared by hydro-solvothermal method (2.6 % Ni-TiO2EG?W?H) showed 92 % selectivity of azoxybenzene with 89 % conversion of nitrobenzene, under mild reaction conditions, which is quite higher as compared to reported non-noble metal catalysts. Prepared catalysts were thoroughly characterized by various analytical techniques to find out the physicochemical characteristic features of the materials. 2.6 % Ni-TiO2EG-W catalyst exhibited highly dispersed nickel nanoparticles (~6.8 nm) over TiO2 surface and strong metal-support interaction due to smaller size of Ni-particles, which significantly enhanced the catalytic efficiency towards selective reduction of nitroarenes to azoxy compounds. Effect of solvents on catalyst synthesis process was also investigated and reported for establishing the superiority of 2.6 % Ni-TiO2EG-W catalyst. The heterogeneous nature of highly dispersed catalyst (2.6 % Ni-TiO2EG-W) was confirmed by the recyclability tests and found that the catalyst particles can be easily recovered and recycled up to four successive runs without any significant loss in its catalytic performance.
- Adak, Shubhadeep,Bal, Rajaram,Bhandari, Sonu,Bordoloi, Ankur,Prasad, V. V. D. N.,Sasaki, Takehiko,Shukla, Astha,Singha, Rajib Kumar
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- A new procedure to azoarene from azoxyarene by ultrasonic dispersed potassium
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Azoarenes were obtained from reduction of the corresponding azoxy- compounds by ultrasonically dispersed potassium under ultrasonic irradiation. The yields depended the substituent group in the phenyl.
- Wang, Xiaolun,Xu, Minghua,Chen, Jijun,Pan, Yi,Shi, Yaozeng
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- Reduction of nitroaromatic compounds on supported gold nanoparticles by visible and ultraviolet light
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Shedding light: Nitroaromatic compounds on gold nanoparticles (3 wt %) supported on ZrO2 can be reduced directly to the corresponding azo compounds when illuminated with visible light or ultraviolet light at 40 °C (see picture). The process occurs with high selectivity and at ambient temperature and pressure, and enables the selection of intermediates that are unstable in thermal reactions. Copyright
- Zhu, Huaiyong,Ke, Xuebin,Yang, Xuzhuang,Sarina, Sarina,Liu, Hongwei
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- Correction to "electrochemically Determined O-H Bond Dissociation Free Energies of NiO Electrodes Predict Proton-Coupled Electron Transfer Reactivity" (Journal of the American Chemical Society (2019)141: 38 (14971-14975)Doi: 10.1021/jacs.9b07923)
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The aqueous CG value used to calculate the bond dissociation free energy (BDFE) values reported in the published Communication was incorrect due to a sign error in its derivation. This systematic error does not affect the conclusions of the study, as all of the aqueous BDFE values shift together. The correct aqueous CG,H2O value is 52.8 kcal mol?1, as reported by Connelly, Wiedner, and Appel.1 We thank Drs. Wiedner and Appel for helpful discussions regarding this correction. We report here revised equations, tables, and schemes with BDFE values adjusted for the correct aqueous CG,H2O term. Pages 14971 and 14972. Equation 1 has been modified to report the correct aqueous CG term, and eqs 4 and 5, which give BDFE values for NiII(OH)2 and NiIIIO(OH), have also been adjusted accordingly. The revised equations are shown below: BDFE(X?H) = 23.06E(pH 0) + 52.8 kcal mol?1 (1) = } =} ? ? Ni O(OH)/Ni (OH) E 0.99 0.03 V BDFE 75.6 1.0 kcal mol III II 2 1 (4) = } = } ? ? Ni O /Ni O(OH) E 1.36 0.02 V BDFE 84.2 1.0 kcal mol IV 2 III 1 (5) Revised BDFE values for the PCET substrates discussed in the original text are given in Table 1. Page 14973. The BDFE ranges discussed in the original publication were adjusted in a similar manner. Thermodynamically favorable reactions at NiIIIO(OH) are predicted for substrates with X?H BDFE less than 75 kcal mol?1 (and were observed for substrates with X?H BDFE ranging from 61 to 73 kcal mol?1). Thermodynamically unfavorable reactivity is predicted (and was observed) for substrates with X?H BDFE greater than 76 kcal mol?1. The observed equilibrium reactivity with 2,4,6-tBu3PhOH is consistent with both the substrate and NiII(OH)2 having an O?H BDFE of ?75.5 kcal mol?1. The number line in Scheme 1 has been adjusted to reflect the corrected BDFE values, and the revised scheme is shown below. [Formula presented] Supporting Information. The BDFE values reported in Tables S1 and S5 were also adjusted for the correct aqueous CG value. The corrected tables are provided in the complete, revised Supporting Information file.
- Wise, Catherine F.,Mayer, James M.
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- 1,5-Diselenacyclo-octane: Synthesis and the First Isolation of the Diselenide PF6- Salt +-Se+R2>
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A new cyclic bis-selenide, 1,5-diselenacyclo-octane (1) has been prepared; two-electron oxidation of (1) with two equivalents of NOPF6 gave a novel diselenide PF6- salt which acts as an oxidizing agent.
- Fujihara, Hisashi,Akaishi, Ryouichi,Erata, Tomoki,Furukawa, Naomichi
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- Chitosan-derived N-doped carbon catalysts with a metallic core for the oxidative dehydrogenation of NH-NH bonds
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Sustainable metal-encased (Ni-Co/Fe/Cu)?N-doped-C catalysts were prepared from bio-waste and used for the oxidative dehydrogenation reaction. A unique combination of bimetals, in situ N doping, and porous carbon surfaces resulted in the formation of the effective "three-in-one" catalysts. These N-doped graphene-like carbon shells with bimetals were synthesized via the complexation of metal salts with chitosan and the subsequent pyrolysis at 700 °C. A well-developed thin-layer structure with large lateral dimensions could be obtained by using Ni-Fe as the precursor. Importantly, the Ni-Fe?N-doped-C catalyst was found to be superior for the dehydrogenation of hydrazobenzene under additive/oxidant-free conditions compared to the conventional and other synthesized catalysts. Characterizations by TEM and XPS accompanied by BET analysis revealed that the enhanced catalytic properties of the catalysts arose from their bimetals and could be attributed to the graphitic shell structure and graphitic N species, respectively.
- Thombal, Priyanka Raju,Thombal, Raju S.,Han, Sung Soo
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- Kinetics of some electron-transfer reactions of iron(III)-2,2′-bipyridyl complex. Micellar effect of sodium dodecyl sulphate
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Iron(III)-2,2′-bipyridyl complex obtained, in situ, by direct mixing of iron(III) and 2,2′-bipyridyl, oxidizes aniline, thiourea, and ascorbic acid. The reaction is markedly accelerated by sodium dodecyl sulphate. The rate-[surfactant] profile exhibits a maximum. The kinetic analysis of the micellar effect has been carried out using Berezin's approach. The binding constants of 2,2′-bipyridyl, aniline, thiourea, and ascorbic acid have been determined.
- Subba Rao,Krishna Rao,Ramakrishna,Rambabu,Satyanarayana
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- Trimethylsilyl-Induced N-O Bond Cleavage in Nitrous Oxide-Derived Aminodiazotates
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The chemical activation of nitrous oxide (N2O) typically results in O-atom transfer and the extrusion of N2 gas. In contrast, reactions of N-trimethylsilyl (TMS)-substituted amides with N2O give inorganic or organic azides
- Liu, Yizhu,Eymann, Léonard Y. M.,Solari, Euro,Fadaei Tirani, Farzaneh,Scopelliti, Rosario,Severin, Kay
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- Electron-excited dioxygen generated by the tri-tert-butoxyaluminum - tert-butyl hydroperoxide system as an efficient oxidant of aniline and some N-substituted anilines
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The tri-tert-butoxyaluminum - tert-butyl hydroperoxide system generates molecular oxygen in the electron-excited singlet state (1O 2), which oxidizes diphenylamine, N-ethylaniline, aniline, and 2,6-diisopropylaniline to form nitroxyl radicals. The latters were identified by ESR at 240-293 K. Oxidation proceeds via the intermediate formation of nitrogen-containing N-peroxide compounds.
- Dodonov,Zaburdaeva,Stepovik,Cherkasov
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- A highly efficient iron doped BaTiO3 nanocatalyst for the catalytic reduction of nitrobenzene to azoxybenzene
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In the present study, we report an efficient and high yielding catalytic reduction of nitrobenzene in the presence of 2-propanol or molecular H 2 over Fe doped BaTiO3 nanocatalysts. This method provides 100% conversion of nitrobenzene with 93% and 95% AOB yield with 2-propanol and molecular H2 under the described experimental conditions, thus leading to efficient synthesis of azoxybenzene from nitrobenzene. The optimum Fe content to obtain high azoxybenzene yields was 2.5% and 10% in the presence of 2-propanol and molecular H2 respectively.
- Srilakshmi,Vijay Kumar,Praveena,Shivakumara,Muralidhar Nayak
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- PHOTOLYSIS OF PHENYL AZIDE
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The quantum yield for the photodissociation of phenyl azide in the concentration range from 10-4 to 10-1 M is 0.4-0.5, while the yield of azobenzene does not exceed 50percent. Keywords: phenyl azide, quantum yield, chain decomposition.
- Budyka, M. F.,Kantor, M. M.,Alfimov, M. V.
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- Reductive reactions of nitroarenes in the presence of allyl bromide and zinc dust
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Under the mild condition, allyl bromide/Zn mediated reductive N,O- diallylation of nitrobenzene was observed. In case of o-nitroarenes such as 2-nitrobenzaldehyde derivatives, 2'-nitroacetophenone, and N-(2- nitrobenzylidene)anilines, reductive cyclizations were accomplished in good to excellent yields. Synthesis and mechanistic details are discussed.
- Kim, Byeong Hyo,Kim, Tae Kyu,Cheong, Jae Wook,Lee, Sang Woo,Jun, Young Moo,Baik, Woonphil,Lee, Byung Min
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- Structure and Reactivity of a High-Spin, Nonheme Iron(III)-Superoxo Complex Supported by Phosphinimide Ligands
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Nonheme iron oxygenases utilize dioxygen to accomplish challenging chemical oxidations. A further understanding of the Fe-O2 intermediates implicated in these processes is challenged by their highly transient nature. To that end, we have developed a ligand platform featuring phosphinimide donors intended to stabilize oxidized, high-spin iron complexes. O2 exposure of single crystals of a three-coordinate Fe(II) complex of this framework allowed for in crystallo trapping of a terminally bound Fe-O2 complex suitable for XRD characterization. Spectroscopic and computational studies of this species support a high-spin Fe(III) center antiferromagnetically coupled to a superoxide ligand, similar to that proposed for numerous nonheme iron oxygenases. In addition to the apparent stability of this synthetic Fe-O2 complex, its ability to engage in a range of stoichiometric and catalytic oxidation processes demonstrates that this iron-phosphinimide system is primed for development in modeling oxidizing bioinorganic intermediates and green oxidation chemistry.
- Field, Mackenzie J.,Lee, Heui Beom,Rittle, Jonathan,Teat, Simon J.,Winslow, Charles
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- Investigating the Hybrid-Structure-Effect of CeO2-Encapsulated Au Nanostructures on the Transfer Coupling of Nitrobenzene
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Due to the obvious distinctions in structure, core–shell nanostructures (CSNs) and yolk–shell nanostructures (YSNs) exhibit different catalytic behavior for specific organic reactions. In this work, two unique autoredox routes are developed to the fabrication of CeO2-encapsulated Au nanocatalysts. Route A is the synthesis of well-defined CSNs by a one-step redox reaction. The process involves an interesting phenomenon in which Ce3+ can act as a weak acid to inhibit the hydrolysis of Ce4+ under the condition of OH? shortage. Route B is the fabrication of monodispersed YSNs by a two-step redox reaction with amorphous Co3O4 as an in situ template. Furthermore, the transfer coupling of nitrobenzene is chosen as a probe reaction to investigate their catalytic difference. The CSNs can gradually achieve the conversion of nitrobenzene into azoxybenzene, while the YSNs can rapidly convert nitrobenzene into azobenzene. The different catalytic results are mainly attributed to their structural distinctions.
- Li, Jian,Song, Shuyan,Long, Yan,Wu, Lanlan,Wang, Xiao,Xing, Yan,Jin, Rongchao,Liu, Xiaogang,Zhang, Hongjie
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- Copper nanoparticles on graphene support: An efficient photocatalyst for coupling of nitroaromatics in visible light
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Copper is a low-cost plasmonic metal. Efficient photocatalysts of copper nanoparticles on graphene support are successfully developed for controllably catalyzing the coupling reactions of aromatic nitro compounds to the corresponding azoxy or azo compounds under visible-light irradiation. The coupling of nitrobenzene produces azoxybenzene with a yield of 90 % at 60 °C, but azobenzene with a yield of 96 % at 90 °C. When irradiated with natural sunlight (mean light intensity of 0.044 W cm-2) at about 35 °C, 70 % of the nitrobenzene is converted and 57 % of the product is azobenzene. The electrons of the copper nanoparticles gain the energy of the incident light through a localized surface plasmon resonance effect and photoexcitation of the bound electrons. The excited energetic electrons at the surface of the copper nanoparticles facilitate the cleavage of the N=O bonds in the aromatic nitro compounds. Hence, the catalyzed coupling reaction can proceed under light irradiation and moderate conditions. This study provides a green photocatalytic route for the production of azo compounds and highlights a potential application for graphene. Green, light-assisted catalysis: Graphene-supported copper nanoparticles are used as photocatalysts. The photocatalysts can controllably reduce nitroaromatics to corresponding azoxy and azo compounds (see picture) under visible-light irradiation. Copyright
- Guo, Xiaoning,Hao, Caihong,Jin, Guoqiang,Zhu, Huai-Yong,Guo, Xiang-Yun
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- A convenient method for dehydrogenation of symmetric hydrazo compounds
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A convenient method using FeCl3 as oxidant to dehydrogenate symmetric hydrazo compounds is reported for the first time. The method is superior to other known methods for dehydrogenating ArNHNHAr . It needs only cheap and less toxic reagents, mild conditions and short reaction time. Eight symmetric azo compounds are prepared in good yields.
- Wang, Cai-Lan,Wang, Xiao-Xia,Wang, Xiao-Yang,Xiao, Jun-Ping,Wang, Yu-Lu
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- Granulated carbon nanotubes as the catalyst support for Pt for the hydrogenation of nitrobenzene
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Granulated Pt/carbon nanotubes (CNTs) were found to have a much better catalytic activity in the liquid phase hydrogenation of nitrobenzene than Pt/activated carbon (AC). The granulated CNTs had much larger pores than the AC particles, which gave a faster mass transfer rate of H2 that helped produce aniline with high selectivity.
- Jin, Shao,Qian, Weizhong,Liu, Yi,Wei, Fei,Wang, Dezeng,Zhang, Jinchang
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- Tying the alkoxides together: An iron complex of a new chelating bulky bis(alkoxide) demonstrates selectivity for coupling of non-bulky aryl nitrenes
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New chelating bis(alkoxide) ligand H2[OO]Ph and its iron(ii) complex Fe[OO]Ph(THF)2 are described. The coordination of the ligand to the metal center is reminiscent of the coordination of two monodentate alkoxides in previously reported Fe(OR)2(THF)2 species. Fe[OO]Ph(THF)2 catalyzes selective and efficient dimerization of non-bulky aryl nitrenes to yield the corresponding azoarenes.
- Kurup, Sudheer S.,Wannipurage, Duleeka,Lord, Richard L.,Groysman, Stanislav
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- Transfer hydrogenation of nitroarenes with hydrazine at near-room temperature catalysed by a MoO2 catalyst
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We present an experimental and computational study of the elementary steps of hydrazine hydrogen transfer on crystalline MoO2, and demonstrate its unique bifunctional metallic-basic properties in a catalytic hydrogenation reaction. Density functional theory (DFT) calculations suggest that the stepwise hydrogen transfer via the prior cleavage of the N-H bond rather than the N-N bond, is the key step to create the dissociated hydride and proton species on the dual Mo and O sites, marking its difference with common oxides. Crystalline MoO2 shows exceptionally high chemoselectivity toward the nitro reduction over C=C, C≡C, and C≡N groups at room temperature and lower, down to 0 °C, rendering it as a promising catalytic material for hydrogenation reactions.
- Zhang, Chaofeng,Lu, Jianmin,Li, Mingrun,Wang, Yehong,Zhang, Zhe,Chen, Haijun,Wang, Feng
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- MECHANISM OF REACTION OF AZOBENZENE FORMATION FROM ANILINE AND NITROSOBENZENE IN BASIC CONDITIONS. GENERAL BASE CATALYSIS BY HYDROXIDE ION
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The reaction of nitrosobenzene with aniline, to give azobenzene, in basic conditions was studied.It was shown that the reaction exhibits general base catalysis by different buffers giving a Broensted coefficient β = 0.318.As in previous studies, a two-step process with a first step of attack of aniline on nitrosobenzene to give an addition intermediate and a second step of dehydration of this intermediate is proposed to interpret the mechanism of the reaction.The analysis of the Broensted relationship and of the intermediate of the reaction led to the suggestion that hydroxide ion catalyses the reaction by a mechanism of general base catalysis in the dehydration step.
- Dalmagro, Jacir,Yunes, Rosendo A.,Simionatto, Edesio Luiz
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- Azoxy- and Azoferrocenes, and N-(Ferrocenylarylmethylene)anilines Formed via Aryliminodimagnesium(IDMg) Procedure. Effect of Ferrocenyl Group on IDMg Reaction and Molecular Structures of Products
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Some unsymmetrical azoxy- and azoferrocenes and N-(ferrocenylarylmethylene)anilines were obtained by the reactions of aryliminodiamagnesium reagents (ArN(MgBr)2) with nitro- and aroylferrocenes.The types of products were same as those obtained in the simi
- Tsutsumi, Toshiki,Okubo, Masao,Yasuoka, Noritake,Katsube, Yukiteru
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- REACTIONS OF SILYL-SUBSTITUTED CARBANIONS WITH NITRONES
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The reaction of carbanions, prepared from 2-(trimethylsilylmethyl)pyridine or N,N-dimethyltrimethylsilylacetamide and lithium diisopropylamide in tetrahydrofuran, with α-aryl-N-phenylnitrones afforded a mixture of corresponding (E)-alkene, azobenzene and azoxybenzene, respectively.On the other hand, the carbanions reacted with cyclic nitrones to give the corresponding aziridine and/or hydroxylamine derivatives as major products.
- Tsuge, Otohiko,Sone, Kazuhiro,Urano, Sathoshi
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- Room temperature selective reduction of nitrobenzene to azoxybenzene over magnetically separable urchin-like Ni/Graphene nanocomposites
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Magnetically recyclable Ni/Graphene (Ni/G) nanocomposites were synthesized via an in situ reduction growth process for selective reduction of nitroarenes into corresponding azoxybenzene at room temperature and at atmospheric pressure. Here, hydrazine hydrate (N2H4H2O) is used as the reducing agent which generates harmless by-products such as N2 and water. The catalyst, when used under controlled reaction conditions, exhibits a 100% conversion and selectivity to the target product without the use of any external additives (turnover number 36.2). Under the optimized conditions, a variety of structurally different nitroarenes were selectively transformed to their corresponding azoxy products in high conversions. Furthermore, a high stability and recyclability of the catalyst were also observed under the investigated conditions (93% conversion, 100% selectivity after the 4th reuse).
- Pahalagedara, Madhavi N.,Pahalagedara, Lakshitha R.,He, Junkai,Miao, Ran,Gottlieb, Becca,Rathnayake, Dinithi,Suib, Steven L.
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- The Reaction of Diazonium Ion Generated from α-Azohydroperoxide with Phenols. The Isolation and Reaction of Diazoether Intermediate
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The reaction of benzenediazonium ion generated from α-azohydroperoxide with 1-naphthol gave a diazoether which rearranged to 2- and 4-phenylazo-1-naphthols.
- Tezuka, Takahiro,Ando, Setsuo,Wada, Toshinori
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- Monodispersed AuPd nanoalloy: Composition control synthesis and catalytic properties in the oxidative dehydrogenative coupling of aniline
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A series of AuPd@C nanoalloy catalysts with tunable compositions were successfully prepared by a co-reduction method. The use of borane-tert-butylamine complex as reductant and oleylamine as both solvent and reductant was very effective for the preparation of the monodispersed nanoalloy. We evaluated the catalytic activity of these AuPd@C nanoalloys for oxidative dehydrogenative coupling of aniline, which showed better catalytic activity than equal amounts of sole Au@C or Pd@C catalyst. The Au1Pd3@C catalyst exhibited the best performance, indicating that the conversion and selectivity were improved along with the increase of Pd composition. However if the Pd composition was too high in the AuPd alloy, Au1Pd7@C achieved only 81% conversion in this reaction.
- Fu, Fangyu,He, Sen,Yang, Sha,Wang, Chen,Zhang, Xun,Li, Peng,Sheng, Hongting,Zhu, Manzhou
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- REACTIONS OF AZOXYBENZENE WITH DICHLOROCARBENE IN THE PHASE-TRANSFER-CATALYZED SYSTEM.
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Azoxybenzene reacted with dichlorocarbene at 40 degree C in the presence of a phase-transfer catalyst (18-crown-6 or tributylamine) in a binary solvent (CHCl//3-aqueous KOH), giving 2,2,3,3-tetrachloro-1-phenylaziridine (4), azobenzene, and 2-hydroxy-1-phenylbenzimidazole.
- Sekiguchi,Fujiu
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- Correlation studies in the oxidation of Vanillin Schiff bases by acid bromate - A kinetic and semi-empirical approach
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Kinetics and mechanistic aspects of oxidation of Vanillin Schiff bases (obtained from Vanillin and p-substituted anilines) by bromate in acid medium has been studied at 313 ?K. The reaction exhibited first order in [bromate] and less than unity order each in [Vanillin Schiff base] and [acid]. The increase in the rate of reaction with decrease in dielectric constant of the medium is observed with all the studied substrates. The reaction failed to induce the polymerization of acrylonitrile. Electron withdrawing substituents in the aniline ring moiety of Vanillin Schiff base accelerate the rate of oxidation to a large extent and electron releasing substituents retard the rate. The order of reactivity is found to be p-nitro ?> ?p-bromo ?> ?p-chloro ?> ?–H ?> ?p-fluoro ?> ?p-methyl ?> ?p-methoxy ?> ?p-ethoxy and the sensitivity of the substrates towards the reaction rate is further supported by the semi-empirical calculation of electronic properties and global descriptors of the substrates (Vanillin Schiff bases) with different substituents in the aniline ring moiety. The observed trend in the reactivity of the substrates was correlated with the calculated descriptors like electronegativity, chemical potential, electrophilicity index, chemical hardness and frontier molecular orbitals. The linear free-energy relationship is characterized by a straight line in the Hammett's plot of log k versus σ. The ρ values are positive and increase with increase in temperature. From the Exner and Arrhenius plots, the isokinetic relationship is discussed. Oxidation products identified are p-substituted azobenzene and vanillic acid. Based on the experimental observations, a plausible mechanism is proposed and rate law is derived.
- Sathish,Teja, P. Ravi,Ramudu, M. Parusha,Manjari, P. Sunitha,Rao, R. Koteshwar
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- Research on the decomposition kinetics and thermal hazards of aniline diazonium salt
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Diazotization reaction, strong exothermic characteristics and thermal instability of diazonium salts make the production process high risk. To research thermal hazards of aniline diazonium salt, dynamic experiments are carried out by the differential scanning calorimeter (DSC) to obtain thermodynamic parameters. Moreover, the kinetic parameters are analyzed by Advanced Kinetics and Technology Solutions (AKTS) software. Finally, the GC-MS and UV spectrum are used to further study the decomposition mechanism of the aniline diazonium salt. The results indicate that aniline diazonium salt is very easy to decompose. When the heating rate is 2 K/min, the onset decomposition temperature is only 27.21 ℃ (Tonset). The apparent activation energy of the decomposition process calculated by Friedman and Ozawa methods are respectively 98-85 kJ/mol and 110-100 kJ/mol. Under the ideal adiabatic conditions (φ = 1), the initial temperatures of TMRad for 24 h is only 6.2 ℃ (TD24), which is predicted by the AKTS software. The decomposition process of aniline diazonium salt is inconsistent with a single reaction mechanism.
- Du, Lei,Wang, Ben,Xie, Chuanxin,Yuan, Yucan
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- α-Diimine synthesis via titanium-mediated multicomponent diimination of alkynes with C-nitrosos
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α-Diimines are commonly used as supporting ligands for a variety of transition metal-catalyzed processes, most notably in α-olefin polymerization. They are also precursors to valuable synthetic targets, such as chiral 1,2-diamines. Their synthesis is usually performed through acid-catalyzed condensation of amines with α-diketones. Despite the simplicity of this approach, accessing unsymmetrical α-diimines is challenging. Herein, we report the Ti-mediated intermolecular diimination of alkynes to afford a variety of symmetrical and unsymmetrical α-diimines through the reaction of diazatitanacyclohexadiene intermediates with C-nitrosos. These diazatitanacycles can be readily accessed in situ via the multicomponent coupling of TiNR imidos with alkynes and nitriles. The formation of α-diimines is achieved through formal [4 + 2]-cycloaddition of the C-nitroso to the Ti and γ-carbon of the diazatitanacyclohexadiene followed by two subsequent cycloreversion steps to eliminate nitrile and afford the α-diimine and a Ti oxo.
- Cheng, Yukun,Egger, Dominic T.,Frye, Connor W.,Kounalis, Errikos,Pearce, Adam J.,Tonks, Ian A.
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p. 1469 - 1477
(2022/02/11)
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- NaI/PPh3-Mediated Photochemical Reduction and Amination of Nitroarenes
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A mild transition-metal- and photosensitizer-free photoredox system based on the combination of NaI and PPh3 was found to enable highly selective reduction of nitroarenes. This protocol tolerates a broad range of reducible functional groups such as halogen (Cl, Br, and even I), aldehyde, ketone, carboxyl, and cyano. Moreover, the photoredox catalysis with NaI and stoichiometric PPh3 provides also an alternative entry to Cadogan-type reductive amination when o-nitrobiarenes were used.
- Qu, Zhonghua,Chen, Xing,Zhong, Shuai,Deng, Guo-Jun,Huang, Huawen
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supporting information
p. 5349 - 5353
(2021/07/21)
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- Azo synthesis meets molecular iodine catalysis
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A metal-free synthetic protocol for azo compound formation by the direct oxidation of hydrazine HN-NH bonds to azo group functionality catalyzed by molecular iodine is disclosed. The strengths of this reactivity include rapid reaction times, low catalyst loadings, use of ambient dioxygen as a stoichiometric oxidant, and ease of experimental set-up and azo product isolation. Mechanistic studies and density functional theory computations offering insight into this reactivity, as well as the events leading to azo group formation are presented. Collectively, this study expands the potential of main-group element iodine as an inexpensive catalyst, while delivering a useful transformation for forming azo compounds.
- Rowshanpour, Rozhin,Dudding, Travis
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p. 7251 - 7256
(2021/02/26)
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- Hydrogen peroxide based oxidation of hydrazines using HBr catalyst
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Azo compounds (RN = NR′) are an important class of organic molecules that find wide application in organic synthesis. Herein, we report an efficient, practical and metal-free oxidation of hydrazines (RNH-NHR’) to azo compounds using 5 mol% HBr and hydrogen peroxide as terminal oxidant. This new method has been demonstrated by 40 examples with excellent yields. In addition, we showcased two examples of the one-pot sequential reactions involving our hydrazine oxidation/hydrolysis/Heck reaction or Cu-catalyzed N-arylation with aryl boronic acid. The distinct advantages of this protocol include metal-free catalysis, waste prevention, and easy operation.
- Du, Wanting,Ma, Zichao,Shao, Liming,Wang, Jian
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- Copper(II)-catalyzed aerobic oxidation of hydrazides to Azo intermediates and their Diels-Alder versus ene trapping
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The oxidation of diethyl 1, 2-hydrazinedicarboxylate using a catalytic Cu(II)-oxazoline system occurs at RT in air, resulting in azo generation, which can then be trapped in situ via hetero-Diels-Alder (HDA) and competitive ene-reactions, with chemoselect
- Chaiyaveij, Duangduan,Whiting, Andrew
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supporting information
(2021/12/01)
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- Sterically Stabilized End-On Superoxocopper(II) Complexes and Mechanistic Insights into Their Reactivity with O-H, N-H, and C-H Substrates
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Instability of end-on superoxocopper(II) complexes, with respect to conversion to peroxo-bridged dicopper(II) complexes, has largely constrained their study to very low temperatures. This limits their kinetic capacity to oxidize substrates. In response, we have developed a series of bulky ligands, Ar3-TMPA (Ar = tpb, dpb, dtbpb), and used them to support copper(I) complexes that react with O2 to yield [CuII(?1-O2?-)(Ar3-TMPA)]+ species, which are stable against dimerization at all temperatures. Binding of O2 saturates at subambient temperatures and can be reversed by warming. The onset of oxygenation for the Ar = tpb and dpb systems is observed at 25 °C, and all three [CuII(?1-O2?-)(Ar3-TMPA)]+ complexes are stable against self-decay at temperatures of ≤-20 °C. This provides a wide temperature window for study of these complexes, which was exploited by performing extensive reaction kinetics measurements for [CuII(?1-O2?-)(tpb3-TMPA)]+ using a broad range of O-H, N-H, and C-H bond substrates. This includes correlation of second order rate constants (k2) versus oxidation potentials (Eox) for a range of phenols, construction of Eyring plots, and temperature-dependent kinetic isotope effect (KIE) measurements. The data obtained indicate that reaction with all substrates proceeds via H atom transfer (HAT), reaction with the phenols proceeds with significant charge transfer, and full tunneling of both H and D atoms occurs in the case of 1,2-diphenylhydrazine and 4-methoxy-2,6-di-tert-butylphenol. Oxidation of C-H bonds proved to be kinetically challenging, and whereas [CuII(?1-O2?-)(tpb3-TMPA)]+ can oxidize moderately strong O-H and N-H bonds, it is only able to oxidize very weak C-H bonds.
- Debnath, Suman,England, Jason,Kr?mer, Tobias,Laxmi, Shoba,Quek, Sebastian Y.,Van Gastel, Maurice
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supporting information
p. 19731 - 19747
(2021/11/30)
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- Reversible Scavenging of Dioxygen from Air by a Copper Complex
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We report that exposing the dipyrrin complex (EMindL)Cu(N2) to air affords rapid, quantitative uptake of O2 in either solution or the solid-state to yield (EMindL)Cu(O2). The air and thermal stability of (EMindL)Cu(O2) is unparalleled in molecular copper-dioxygen coordination chemistry, attributable to the ligand flanking groups which preclude the [Cu(O2)]1+ core from degradation. Despite the apparent stability of (EMindL)Cu(O2), dioxygen binding is reversible over multiple cycles with competitive solvent exchange, thermal cycling, and redox manipulations. Additionally, rapid, catalytic oxidation of 1,2-diphenylhydrazine to azoarene with the generation of hydrogen peroxide is observed, through the intermittency of an observable (EMindL)Cu(H2O2) adduct. The design principles gleaned from this study can provide insight for the formation of new materials capable of reversible scavenging of O2 from air under ambient conditions with low-coordinate CuI sorbents.
- Betley, Theodore A.,Carsch, Kurtis M.,Iliescu, Andrei,Mason, Jarad A.,McGillicuddy, Ryan D.
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supporting information
p. 18346 - 18352
(2021/11/10)
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- Manganese Catalyzed Hydrogenation of Azo (N=N) Bonds to Amines
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We report the first example of homogeneously catalyzed hydrogenation of the N=N bond of azo compounds using a complex of an earth-abundant-metal. The hydrogenation reaction is catalyzed by a manganese pincer complex, proceeds under mild conditions, and yields amines, which makes this methodology a sustainable alternative route for the conversion of azo compounds. A plausible mechanism involving metal-ligand cooperation and hydrazine intermediacy is proposed based on mechanistic studies. (Figure presented.).
- Ben-David, Yehoshoa,Das, Uttam Kumar,Diskin-Posner, Yael,Kar, Sayan,Milstein, David
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supporting information
p. 3744 - 3749
(2021/07/09)
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- Chemoselective Hydrogenation of Nitroarenes Using an Air-Stable Base-Metal Catalyst
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The reduction of nitroarenes to anilines as well as azobenzenes to hydrazobenzenes using a single base-metal catalyst is reported. The hydrogenation reactions are performed with an air-and moisture-stable manganese catalyst and proceed under relatively mild reaction conditions. The transformation tolerates a broad range of functional groups, affording aniline derivatives and hydrazobenzenes in high yields. Mechanistic studies suggest that the reaction proceeds via a bifunctional activation involving metal-ligand cooperative catalysis.
- Zubar, Viktoriia,Dewanji, Abhishek,Rueping, Magnus
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p. 2742 - 2747
(2021/05/05)
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- The relationship of morphology and catalytic performance of CeO2 catalysts for reducing nitrobenzene to azoxybenzene under the base-free condition
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CeO2 morphology was proposed to be a crucial factor for reducing nitrobenzene to azoxybenzene under the base-free condition. Herein, the structure-activity relationship of CeO2 catalysts was explored to improve the azoxybenzene yield. A series of CeO2 catalysts were synthesized with seven morphologies to obtain different Ce3+ proportion and various surface areas. Notably, the catalytic performance of these samples for reducing nitrobenzene to azoxybenzene enhanced with the increasing Ce3+ proportion. With the highest surface Ce3+ proportion, the Rod-CeO2 catalyst exhibited 100% conversion of nitrobenzene and 89.8% azoxybenzene selectivity in 7 h at 150 °C under 1 MPa CO. Moreover, the preliminary mechanistic analysis indicated that the inhabitation of azoxybenzene to by-product azobenzene resulted in the high selectivity of azoxybenzene.
- Zhou, Xueke,Zhao, Haitao,Liu, Shaojun,Yang, Yang,Qu, Ruiyang,Zhen, Chenghang,Gao, Xiang
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supporting information
p. 761 - 764
(2020/07/17)
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- Selective Oxidation of Anilines to Azobenzenes and Azoxybenzenes by a Molecular Mo Oxide Catalyst
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Aromatic azo compounds, which play an important role in pharmaceutical and industrial applications, still face great challenges in synthesis. Herein, we report a molybdenum oxide compound, [N(C4H9)4]2[Mo6O19] (1), catalyzed selective oxidation of anilines with hydrogen peroxide as green oxidant. The oxidation of anilines can be realized in a fully selectively fashion to afford various symmetric/asymmetric azobenzene and azoxybenzene compounds, respectively, by changing additive and solvent, avoiding the use of stoichiometric metal oxidants. Preliminary mechanistic investigations suggest the intermediacy of highly active reactive and elusive Mo imido complexes.
- Han, Sheng,Cheng, Ying,Liu, Shanshan,Tao, Chaofu,Wang, Aiping,Wei, Wanguo,Yu, Han,Wei, Yongge
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supporting information
p. 6382 - 6385
(2021/02/09)
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- A synthetic method of aromatic azo compounds
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The present invention belongs to the field of azo compound technology, discloses a method of synthesis of an aromatic azo compound. The present invention is an aromatic amine and a catalyst massager ratio 1: 0.05 ~ 0.06 mixed, at 95 ~ 110 ° C reaction 22
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Paragraph 0046-0053
(2022/01/05)
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- Photocatalytic oxidative coupling of arylamines for the synthesis of azoaromatics and the role of O2 in the mechanism
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The photocatalytic oxidative coupling of aryl amines to selectively synthesize azoaromatic compounds has been realized. Multiple different photocatalysts can be used to perform the general reaction; however, Ir(dF-CF3-ppy)2(dtbpy)+, where dF-CF3-ppy is 2-(2,4-difluorophenyl)-5-(trifluoromethyl)-pyridine and dtpby is 4,4′-tert-butyl-2,2′-bipyridine, showed the greatest range of reactivity with various amine substrates. Both electron-rich and -deficient amines can be coupled with yields up to 95% under an ambient air atmosphere. Oxygen was deemed to be essential for the reaction and is utilized in the regeneration of the photocatalyst. Fluorescence quenching and radical trap experiments indicate an amine radical coupling mechanism that proceeds through a hydrazoaromatic intermediate before further oxidation occurs to form the desired azoaromatic products.
- Sitter, James D.,Vannucci, Aaron K.
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supporting information
p. 2938 - 2943
(2021/03/01)
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- Invisible Silver Guests Boost Order in a Framework That Cyclizes and Deposits Ag3Sb Nanodots
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The infusion of metal guests into (i.e., metalating) the porous medium of metal-organic frameworks (MOFs) is a topical approach to wide-ranging functionalization purposes. We report the notable interactions of AgSbF6 guests with the designer MOF host ZrL1 [Zr6O4(OH)7(L1)4.5(H2O)4]. (1) The heavy-atom guests of AgSbF6 induce order in the MOF host to allow the movable alkyne side arm to be fully located by X-ray diffraction, but they themselves curiously remain highly disordered and absent in the strucutral model. The enhanced order of the framework can be generally ascribed to interaction of the silver guests with the host alkyne and thioether functions, while the invisible heavy-atom guest represents a new phenomenon in the metalation of open framework materials. (2) The AgSbF6 guests also participate in the thermocyclization of the vicinal alkyne units of the L1 linker (at 450 °C) and form the rare nanoparticle of Ag3Sb supported on the concomitantly formed nanographene network. The resulted composite exhibits high electrical conductivity (1.0 S/cm) as well as useful, mitigated catalytic activity for selectively converting nitroarenes into the industrially important azo compounds, i.e., without overshooting to form the amine side products. The heterogeneous/cyclable catalysis entails only the cheap reducing reagents of NaBH4, ethanol, and water, with yields being generally close to 90%.
- Ahn, Dohyun,Cheng, Shengxian,Feng, Weijin,He, Jun,Hu, Jieying,Xin, Yinger,Xu, Zhengtao,Zeller, Matthias
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supporting information
p. 5757 - 5763
(2021/05/04)
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- Chemoselective electrochemical reduction of nitroarenes with gaseous ammonia
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Valuable aromatic nitrogen compounds can be synthesized by reduction of nitroarenes. Herein, we report electrochemical reduction of nitroarenes by a protocol that uses inert graphite felt as electrodes and ammonia as a reductant. Depending on the cell voltage and the solvent, the protocol can be used to obtain aromatic azoxy, azo, and hydrazo compounds, as well as aniline derivatives with high chemoselectivities. The protocol can be readily scaled up to >10 g with no decrease in yield, demonstrating its potential synthetic utility. A stepwise cathodic reduction pathway was proposed to account for the generations of products in turn.
- Chang, Liu,Li, Jin,Wu, Na,Cheng, Xu
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supporting information
p. 2468 - 2472
(2021/04/02)
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- Single crystal MnOOH nanotubes for selective oxidative coupling of anilines to aromatic azo compounds
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Catalytic synthesis of aromatic azo compounds by oxidative coupling of anilines using molecular oxygen represents a facile, green and valuable process; however, such an economical process suffers from poor catalytic activity and selectivity. Herein, novel single crystal MnOOH nanotubes with abundant Mn3+sites and high oxygen defects were successfully synthesized. The catalyst exhibited high selectivity for oxidative coupling of anilines, achieving complete transformation into aromatic azo compounds under mild conditions, even at room temperature.
- Cao, Fangxian,Li, Jiayuan,Qu, Yongquan,Zhang, Mingkai,Zhang, Sai,Zou, Yong
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supporting information
p. 19692 - 19697
(2021/09/20)
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- Ultrathin ZnTi-LDH nanosheets for photocatalytic aerobic oxidation of aniline based on coordination activation
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In this work, ZnTi-LDH nanosheets with several monolayer thickness were prepared as photocatalysts for the aerobic oxidation of aniline to yield nitrosobenzene under visible light irradiation. UV-vis DRS, in situ FTIR and XPS results jointly revealed that aniline molecules were efficiently chemisorbed and activated on ZnTi-LDH to form surface coordination active species, improving visible light absorption and inducing the photocatalytic reaction. The surface OH groups on ZnTi-LDH as the Br?nsted base sites facilitated the reductive deprotonation of aniline to form the anilino anion, which was a key step in promoting aniline oxidation. ESR and XPS data suggested that oxygen vacancies (OVs) were formed due to the interaction between exposed OH groups and aniline molecules. The OVs, as the centers to capture photoelectrons, achieve the reduction of oxygen molecules to O2- radicals, which further oxidize anilino species to produce nitrosobenzene. Finally, a possible mechanism was proposed to reveal the photocatalytic process based on the surface coordination activation theory. This journal is
- Liu, Cheng,Guo, Wei,Chen, Jinsong,Zou, Junhua,Wang, Zhiwen,Wu, Ling
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p. 162 - 170
(2021/01/28)
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- SO2F2-mediated oxidation of primary and tertiary amines with 30% aqueous H2O2 solution
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A highly efficient and selective oxidation of primary and tertiary amines employing SO2F2/H2O2/base system was described. Anilines were converted to the corresponding azoxybenzenes, while primary benzylamines were transformed into nitriles and secondary benzylamines were rearranged to amides. For tertiary amine substrates quinolines, isoquinolines and pyridines, their oxidation products were the corresponding N-oxides. The reaction conditions are very mild and just involve SO2F2, amines, 30% aqueous H2O2 solution, and inorganic base at room temperature. One unique advantage is that this oxidation system is just composed of inexpensive inorganic compounds without the use of any metal and organic compounds.
- Liao, Xudong,Zhou, Yi,Ai, Chengmei,Ye, Cuijiao,Chen, Guanghui,Yan, Zhaohua,Lin, Sen
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supporting information
(2021/11/01)
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- Supported CuII Single-Ion Catalyst for Total Carbon Utilization of C2 and C3 Biomass-Based Platform Molecules in the N-Formylation of Amines
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The shift from fossil carbon sources to renewable ones is vital for developing sustainable chemical processes to produce valuable chemicals. In this work, value-added formamides were synthesized in good yields by the reaction of amines with C2 and C3 biomass-based platform molecules such as glycolic acid, 1,3-dihydroxyacetone and glyceraldehyde. These feedstocks were selectively converted by catalysts based on Cu-containing zeolite 5A through the in situ formation of carbonyl-containing intermediates. To the best of our knowledge, this is the first example in which all the carbon atoms in biomass-based feedstocks could be amidated to produce formamide. Combined catalyst characterization results revealed preferably single CuII sites on the surface of Cu/5A, some of which form small clusters, but without direct linking via oxygen bridges. By combining the results of electron paramagnetic resonance (EPR) spin-trapping, operando attenuated total reflection (ATR) IR spectroscopy and control experiments, it was found that the formation of formamides might involve a HCOOH-like intermediate and .NHPh radicals, in which the selective formation of .OOH radicals might play a key role.
- Brückner, Angelika,Dai, Xingchao,Kreyenschulte, Carsten,Rabeah, Jabor,Shi, Feng,Wang, Xinzhi
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p. 16889 - 16895
(2021/09/25)
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- TEMPO catalyzed oxidative dehydrogenation of hydrazobenzenes to azobenzenes
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A metal-free direct oxidative dehydrogenation approach for the synthesis of azobenzenes from hydrazobenzenes has been developed by using TEMPO as an organocatalyst for the first time. The reaction proceeded in open air under mild reaction conditions. A wide range of hydrazobenzenes readily undergo dehydrogenation to give the corresponding azobenzenes in excellent yields.
- Fan, Baomin,Laishram, Ronibala Devi,Li, Jiayan,Luo, Yang,Lv, Haiping,More, Sagar,Su, Zhimin,Xu, Dandan,Yang, Yong,Zhan, Yong
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supporting information
p. 3471 - 3474
(2020/05/25)
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- Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence
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Metal ligand cooperativity is a powerful strategy in transition metal chemistry. This type of mechanism for the activation of O2 is best exemplified by heme centers in biological systems. While aerobic oxidations with Fe and Cu are well precedented, Ni-based oxidations are frequently less common due to less-accessible metal-based redox couples. Some Ni enzymes utilize special ligand environments for tuning the Ni(II)/(III) redox couple such as strongly donating thiolates in Ni superoxide dismutase. A recently characterized example of a Ni-containing protein, however, suggests an alternative strategy for mediating redox chemistry with Ni by utilizing ligand-based reducing equivalents to enable oxygen binding. While this mechanism has little synthetic precedent, we show here that Ni complexes of the redox-active ligand tBu,TolDHP (tBu,TolDHP = 2,5-bis((2-t-butylhydrazono)(p-tolyl)methyl)-pyrrole) activate O2 to generate a Ni(II) superoxo complex via ligand-based electron transfer. This superoxo complex is competent for stoichiometric oxidation chemistry with alcohols and hydrocarbons. This work demonstrates that coupling ligand-based redox chemistry with functionally redox-inactive Ni centers enables oxidative transformations more commonly mediated by metals such as Fe and Cu.
- Anderson, John S.,Filatov, Alexander S.,Jesse, Kate A.,Mcneece, Andrew J.,Xie, Jiaze
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supporting information
p. 10824 - 10832
(2020/07/04)
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- Selective oxidation of aniline into azoxybenzene catalyzed by Nb-peroxo@iron oxides at room temperature
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Oxidation of aniline into valuable products such as azoxybenzene, azobenzene, and nitrobenzene has been a great challenge due to the difficulty of controlling the selectivity of heterogeneous catalysts to form the desired products. In this work, an active and selective heterogeneous catalyst for the oxidation of aniline into azoxybenzene was designed by doping iron oxide supports with niobium and immobilizing Nb-peroxo groups on their surfaces through H2O2treatment. The Nb-peroxo groups on the iron oxide support were essential to catalyze the conversion of aniline into products while the niobium favored the formation of azoxybenzene. Among the alcoholic solvents studied, 1-propanol was the most suitable to get high conversion rates of aniline and high selectivity to azoxybenzene. At 3 h reaction time, the Nb-peroxo@iron oxides led to oxidation of aniline with a conversion rate of 99.6% and 83.7% selectivity to azoxybenzene at room temperature. Since the selective and catalytic oxidation of aniline is very important for the synthesis of intermediates and precursors to various industrially valuable products, the results shown herein may contribute to the development of most stable, selective, and active catalysts under mild reaction conditions.
- Lima, André L. D.,Fajardo, Humberto V.,Nogueira, André E.,Pereira, Márcio C.,Oliveira, Luiz C. A.,de Mesquita, Jo?o Paulo,Silva, Adilson C.
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p. 8710 - 8717
(2020/06/08)
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- Efficient and Selective Oxidation of Aromatic Amines to Azoxy Derivatives over Aluminium and Gallium Oxide Catalysts with Nanorod Morphology
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Aluminium oxide and gallium oxide nanorods were identified as highly efficient heterogeneous catalysts for the selective oxidation of aromatic amines to azoxy compounds using hydrogen peroxide as environmentally friendly oxidant. This is the first report of the selective oxidation of aromatic amines to their azoxy derivatives without using transition metal catalysts. Among the tested transition-metal-free oxides, gallium oxide nanorods with small dimensions (9–52 nm length and 3–5 nm width) and fully accessible, high surface area (225 m2 g?1) displayed the best catalytic performance in terms of substrate versatility, activity and azoxybenzene selectivity. Furthermore, the catalyst loading, hydrogen peroxide type (aqueous or anhydrous), and the amount of solvent were tuned to optimise the catalytic performance, which allowed reaching almost full selectivity (98 %) towards azoxybenzene at high aniline conversion (94 %). Reusability tests showed that the gallium oxide nanorod catalyst can be recycled in consecutive runs with complete retention of the original activity and selectivity.
- Singh, Bhawan,Mandelli, Dalmo,Pescarmona, Paolo P.
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p. 593 - 601
(2019/11/13)
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- Efficient chemoselective hydrogenation of nitrobenzene to aniline, azoxybenzene and azobenzene over CQDs/ZnIn2S4 nanocomposites under visible light
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Efficient production of amino-, azo- and azoxy- aromatics is important in chemical industries. In this manuscript, we reported that controllable chemoselective hydrogenation of nitrobenzene to produce aniline, azoxybenzene and azobenzene was realized over CQDs/ZnIn2S4 nanocomposite under visible light via simply regulating the reaction medium including the alkalinity and the hydrogen source. An optimized production of aniline was obtained over 3.0 wt% CQDs/ZnIn2S4 nanocomposite in a reaction medium of TEOA: MeOH (1:1), while a strong alkaline reaction medium promote N-N coupling to produce azoxybenzene and azobenzene. In addition, azoxybenzne is the intermediate to form azobenzene during the hydrogenation of nitrobenzene, in which a strong hydrogen source like TEOA is indispensable for the transformation. This study not only demonstrated a noble metal-free photocatalytic system for visible light induced efficient and controllable chemoselective hydrogenation of nitrobenzene to produce aniline, azobenzene and azoxybenzene, but also highlights the great potential of photocatalysis in organic syntheses.
- Deng, Zirong,Li, Zhaohui,Wang, Bingqing
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p. 241 - 246
(2020/06/27)
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- Intermetallic Nanocatalysts from Heterobimetallic Group 10-14 Pyridine-2-thiolate Precursors
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Intermetallic compounds are atomically ordered inorganic materials containing two or more transition metals and main-group elements in unique crystal structures. Intermetallics based on group 10 and group 14 metals have shown enhanced activity, selectivity, and durability in comparison to simple metals and alloys in many catalytic reactions. While high-temperature solid-state methods to prepare intermetallic compounds exist, softer synthetic methods can provide key advantages, such as enabling the preparation of metastable phases or of smaller particles with increased surface areas for catalysis. Here, we study a generalized family of heterobimetallic precursors to binary intermetallics, each containing a group 10 metal and a group 14 tetrel bonded together and supported by pincer-like pyridine-2-thiolate ligands. Upon thermal decomposition, these heterobimetallic complexes form 10-14 binary intermetallic nanocrystals. Experiments and density functional theory (DFT) computations help in better understanding the reactivity of these precursors toward the synthesis of specific intermetallic binary phases. Using Pd2Sn as an example, we demonstrate that nanoparticles made in this way can act as uniquely selective catalysts for the reduction of nitroarenes to azoxyarenes, which highlights the utility of the intermetallics made by our method. Employing heterobimetallic pincer complexes as precursors toward binary nanocrystals and other metal-rich intermetallics provides opportunities to explore the fundamental chemistry and applications of these materials.
- Adamson, Marquix A. S.,Chen, Yunhua,Daniels, Carena L.,Dorn, Rick W.,Fan, Huajun,Knobeloch, Megan,Rossini, Aaron J.,Vela, Javier,Wu, Hao,Yox, Philip,Zhou, Guoquan
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- Synthesis of phenazines from ortho-bromo azo compounds via sequential Buchwald-Hartwig amination under micellar conditions and acid promoted cyclization
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Non-symmetric phenazines were synthesized via the Buchwald-Hartwig amination of ortho-bromoazobenzenes with anilines under micellar conditions, using the commercially available surfactant Kolliphor EL in water, followed by an acid-promoted 6π-electrocyclization-aromatization process. Two different synthetic pathways to obtain the ortho-bromo azo intermediates were explored, namely the palladium catalysed selective ortho bromination of azobenzenes and the diazo coupling of ortho-bromo diazonium salts with N,N-dimethylaniline, imidazole, phenol, sodium methanesulfinate and ethyl chloroformate.
- Yousif, Dawod,Monti, Mauro,Papagni, Antonio,Vaghi, Luca
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supporting information
(2020/10/19)
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- In vitro biological, catalytic, and DFT studies of some iron(III) N-ligated complexes
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Fe(III) complexes, [Fe(CH3CN)6][X]3 and [Fe(CH3CH2CN)6][X]3 (where X: counter anion = B{C6H3(m-CF3)2}4)? and B(C
- Hijazi, Ahmed K.,Taha, Ziyad A.,Ababneh, Taher S.,Alshare, Heba M.,Al-Bataineh, Nezar,Al-Momani, Waleed M.,Ajlouni, Abdulaziz M.
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p. 1561 - 1572
(2019/12/02)
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- Site-specific catalytic activities to facilitate solvent-free aerobic oxidation of cyclohexylamine to cyclohexanone oxime over highly efficient Nb-modified SBA-15 catalysts
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The development of highly active and selective heterogeneous catalysts for efficient oxidation of cyclohexylamine to cyclohexanone oxime is a challenge associated with the highly sensitive nitrogen center of cyclohexylamine. In this work, dispersed Nb oxide supported on SBA-15 catalysts are disclosed to efficiently catalyze the selective oxidation of cyclohexylamine with high conversion (>75%) and selectivity (>84%) to cyclohexanone oxime by O2without any addition of solvent (TOF = 469.8 h?1, based on the molar amount of Nb sites). The role of the active-site structure identity in dictating the site-specific catalytic activities is probed with the help of different reaction and control conditions and multiple spectroscopy methods. Complementary to the experimental results, further poisoning tests (with KSCN or dehydroxylation reagents) and DFT computational studies clearly unveil that the surface exposed active centers toward activation of the reactants are quite different: the surface -OH groups can catch the NH2group from cyclohexylamine by forming a hydrogen bond and lead to a more facile cyclohexylamine oxidation to desired products, while the monomeric or oligomeric Nb sites with a highly distorted structure play a key role in the dissociation of O2molecules beneficial for insertion of active oxygen species into cyclohexylamine. These catalysts exhibit not only satisfactory recyclability for cyclohexylamine oxidation but also efficiently catalyze the aerobic oxidation of a wide range of amines under solvent-free conditions.
- Ding, Wei,Mao, Liqiu,Peng, Haoyu,Yin, Dulin,Zhong, Wenzhou
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p. 3409 - 3422
(2020/06/09)
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- Tandem selective reduction of nitroarenes catalyzed by palladium nanoclusters
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We report a catalytic tandem reduction of nitroarenes by sodium borohydride (NaBH4) in aqueous solution under ambient conditions, which can selectively produce five categories of nitrogen-containing compounds: anilines, N-aryl hydroxylamines, azoxy-, azo- and hydrazo-compounds. The catalyst is in situ-generated ultrasmall palladium nanoclusters (Pd NCs, diameter of 1.3 ± 0.3 nm) from the reduction of Pd(OAc)2 by NaBH4. These highly active Pd NCs are stabilized by surface-coordinated nitroarenes, which inhibit the further growth and aggregation of Pd NCs. By controlling the concentration of Pd(OAc)2 (0.1-0.5 mol% of nitroarene) and NaBH4, the water/ethanol solvent ratio and the tandem reaction sequence, each of the five categories of N-containing compounds can be obtained with excellent yields (up to 98%) in less than 30 min at room temperature. This tunable catalytic tandem reaction works efficiently with a broad range of nitroarene substrates and offers a green and sustainable method for the rapid and large-scale production of valuable N-containing chemicals.
- Yan, Ziqiang,Xie, Xiaoyu,Song, Qun,Ma, Fulei,Sui, Xinyu,Huo, Ziyu,Ma, Mingming
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supporting information
p. 1301 - 1307
(2020/03/11)
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- Photochemical catalytic synthesis method of aromatic azo compound
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The invention belongs to the field of photochemical organic synthesis, and particularly relates to a photochemical catalytic synthesis method of an aromatic azo compound, which comprises the followingstep: in the presence of light, a photocatalyst, a cocatalyst, a ligand, an alkali and a hydrogen donor, carrying out a deoxidation coupling reaction on a nitro-substituted aromatic compound to obtain the aromatic azo compound. According to the reaction system, the nitro-substituted aromatic compound can be selectively deoxidized and coupled to obtain the aromatic azo compound, and the highest yield of the product can reach 85% or above.
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Paragraph 0055-0056
(2020/05/02)
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- Study of the versatility of CuBTC?IL-derived materials for heterogeneous catalysis
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The versatility of CuBTC (or HKUST-1) MOF materials to be functionalized to tune their catalytic activity performance was evaluated. The MOFs were functionalized with ionic liquids (ILs) to give rise to catalysts able to adsorb CO2and react with epoxides to produce carbonates. The materials are active for this reaction and show good conversion rates at 100 °C and 7 bar CO2, confirming their ability to fix this gas and transform it into valuable products. In addition, the MOF?IL composite material1can be functionalized to give rise to a bimetallic catalyst, taking advantage of the N-heterocyclic carbene present in the imidazolium-based ILs. Therefore, the material was reacted with palladium dichloride, yielding CuBTC?IL-(NHC)Pd (1Pd) which has been tested for homocoupling of alkynes and imination of benzyl alcohol reactions. The recyclability of the catalysts has been studied and hot filtration tests have been made.
- Arriortua, Maria I.,Fernández de Luis, Roberto,Fidalgo-Marijuan, Arkaitz,Iglesias, Marta,Larrea, Edurne S.,Maya, Eva M.
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p. 2904 - 2913
(2020/05/18)
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- One-pot imine synthesis from methylarenes and anilines under air over heterogeneous Cu oxide-modified CeO2catalyst
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Cu oxide-modified CeO2 (CuOx-CeO2) with 2 wtpercent Cu loading amount was the most effective and reusable heterogeneous catalyst for selective one-pot imine synthesis from methylarenes and anilines via direct oxidation of the sp3 C-H bond in the methylare
- Tamura, Masazumi,Li, Yingai,Tomishige, Keiichi
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supporting information
p. 7337 - 7340
(2020/07/23)
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- Nanocomposite-based inorganic-organocatalyst Cu(II) complex and SiO2- and Fe3O4 nanoparticles as low-cost and efficient catalysts for aniline and 2-aminopyridine oxidation
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Bis-imino Cu(II) complex (CuLAn2), in which the imine ligand (HLAn) acts as a bidentate chelating ligand, was synthesized. The catalytic potential of the inorganic-organocatalyst was studied homogeneously and heterogeneously in the oxidation of aniline and 2-aminopyridine by H2O2 or tBuOOH. Two heterogeneous inorganic-organocatalysts, CuLAn2@Fe3O4 and CuLAn2@SiO2@Fe3O4, were synthesized by the successful immobilization of CuLAn2 on the Fe3O4 surface and the composited Fe3O4 with SiO2, respectively. The heterogeneous structure of those inorganic-organocatalysts was confirmed using Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic properties. The adsorption–desorption isotherms revealed respectable adsorption parameters (SBET, Vp, and rp). All catalysts exhibited high potential in the oxidation of aniline (with phenylhydroxylamine as the main product) and good potential in the oxidation of 2-aminopyridine, in the first attempt (with 2-nitropyridine-N-oxide and 2-nitrosopyridine-N-oxide as main products), at room temperature. Acetonitrile was found to be the best solvent compared to ethanol, dimethyl sulfoxide, chloroform, and water. The homogeneous catalyst exhibited reusability for three times. The heterogeneous catalysts, CuLAn2@Fe3O4 and CuLAn2@SiO2@Fe3O4, were active for five and seven times, respectively. A mechanism was proposed within electron and oxygen transfer processes.
- Adam, Mohamed Shaker S.,Al-Omair, Mohammed A.
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- EffectiveN-methylation of nitroarenes with methanol catalyzed by a functionalized NHC-based iridium catalyst: a green approach toN-methyl amines
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Compound [IrBr(CO)2(κC-tBuImCH2PyCH2OMe)] featuring a flexible pyridine/OMe functionalized NHC ligand κ1C coordinated efficiently catalyzes the selectiveN-monomethylation of nitroarenes using methanol as both the reducing agent and the C1 source. A range of functionalized nitroarenes including heterocyclic or sterically hindered derivatives have been efficiently converted to the correspondingN-monomethyl amines in good yields at low catalyst loadings using sub-stoichiometric amounts of Cs2CO3as a base. Mechanistic investigations support a borrowing-hydrogen mechanism in which methanol acts as the hydrogen source and methylating agent. Further, the hydrogen transfer reduction of nitrobenzene to aniline under optimized reaction conditions should proceed through a direct mechanism involving nitrosobenzene andN-phenylhydroxylamine intermediates.
- González-Lainez, Miguel,Jiménez, M. Victoria,Passarelli, Vincenzo,Pérez-Torrente, Jesús J.
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p. 3458 - 3467
(2020/06/17)
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- The importance of copper placement in chiral catalysts supported on heteropolyanions: Lacunary vs external exchanged
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Lacunary [PCuW11O39]5? species modified with chiral bis(oxazoline) leads to very poor results as catalyst in the enantioselective cyclopropanation, in contrast with the Cu-bis(oxazoline) complex exchanged on the Keggin [PW12O40]3? species. The incomplete neutralization and/or exchange of the Keggin species produces a loss in symmetry that leads to spectra in solid phase (IR and NMR) similar to those obtained for the lacunary species. The symmetry is averaged in solution, but additional characterization methods are necessary to determine the true nature of the solid heteropolyanionic species. These results demonstrate that the efficiency of copper-bis(oxazoline) complexes is related to its placement in an external exchange position, whereas the copper included in the heteropolyanion structure is not active for cyclopropanation reactions.
- Fraile, José M.,Mansilla, Daniela S.,Mayoral, José A.,Torviso, M. Rosario
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- Photocatalyzed oxidative dehydrogenation of hydrazobenzenes to azobenzenes
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Visible light mediated oxidative dehydrogenation of hydrazobenzenes under an ambient atmosphere using an organic dye as a photocatalyst was reported for the first time. The reaction provides an environmentally benign method for the preparation of azobenzenes in excellent yields with good functional group tolerance.
- Lv, Haiping,Laishram, Ronibala Devi,Li, Jiayan,Zhou, Yongyun,Xu, Dandan,More, Sagar,Dai, Yuze,Fan, Baomin
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supporting information
p. 4055 - 4061
(2019/08/07)
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- Reactions between 5-Nitroso-1,3-diphenyltetrazolium salts and electron-rich arenes, amines, thiophenol, sulfoxides, and thioanisole
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A series of reactions between 5-nitroso-1,3-diphenyltetrazo-lium tetrafluoroborate and methoxybenzenes, amines, thiols, sulfoxides, and sulfides, most of which are generally accepted as being inert to nitroso groups, is reported here. The tetrazolium-activated nitroso functionality is capable of oxidizing the aforementioned substrates to give the corresponding oxidized products, and the nitroso tetrazolium itself is transformed into the corresponding amide or hydroxyamide, depending on the nature of the reaction partners. In the case of thioanisole, an addition product was obtained.
- Matsukawa, Yuta,Hirashita, Tsunehisa,Araki, Shuki
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supporting information
p. 540 - 544
(2019/04/05)
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- Method for oxidizing and synthesizing azo compounds by taking hydrazine compounds as raw materials
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The invention provides a method for synthesizing azo compounds, and the method takes hydrazine compounds as raw materials and trichloroisocyanuric acid as an oxidant to synthesize the azo compounds ina one-pot high-yield and high-efficiency manner in an organic solvent in an air atmosphere at room temperature. According to the method, the trichloroisocyanuric acid, which is low in price, green, nontoxic and highly efficient in oxidation, is used as the oxidant, and the trichloroisocyanuric acid is low in price, green and environment-friendly, stable in performance and high in use safety; thereaction solvent does not need special treatment, no byproduct is generated, the post reaction treatment is simple, the environmental pollution is small, the method is green and environment-friendly,and the method is suitable for industrial production.
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Paragraph 0018
(2019/08/02)
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- T BuOK-triggered bond formation reactions
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Recently, inexpensive and readily available tBuOK has seen widespread use in transition-metal-free reactions. Herein, we report the use of tBuOK for S-S, S-Se, NN and CN bond formations, which significantly extends the scope of tBuOK in chemical synthesis. Compared with traditional methods, we have realized mild and general methods for disulfide, azobenzenes imine etc. synthesis.
- Xu, Yulong,Shi, Xiaonan,Wu, Lipeng
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p. 24025 - 24029
(2019/08/13)
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- Visible-light-promoted oxidative dehydrogenation of hydrazobenzenes and transfer hydrogenation of azobenzenes
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Azo compounds are widely used in the pharmaceutical and chemical industries. Here, we report the use of a non-metal photo-redox catalyst, Eosin Y, to synthesize azo compounds from hydrazine derivatives. The use of visible-light with air as the oxidant makes this process sustainable and practical. Moreover, the visible-light-driven, photo-redox-catalyzed transfer hydrogenation of azobenzenes is compatible with a series of hydrogen donors such as phenyl hydrazine and cyclic amines. Compared with traditional (thermal/transition-metal) methods, our process avoids the issue of over-reduction to aniline, which extends the applicability of photo-redox catalysis and confirms it as a useful tool for synthetic organic chemistry.
- Wang, Xianya,Wang, Xianjin,Xia, Chungu,Wu, Lipeng
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supporting information
p. 4189 - 4193
(2019/08/07)
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- Preparation method of aromatic azo organic compounds
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The invention discloses a preparation method of aromatic azo compounds so as to achieve high-yield preparation of the azo compounds from diaryl hydrazine low in cost and easy to obtain through oxydehydrogenation by an organic oxidant. According to different raw materials, the symmetrical or asymmetric azo compounds can be obtained, a catalyst is not needed, the reaction raw materials and the organic oxidant are low in cost and easy to obtain, conditions are mild and efficient, a reaction can be complete through only a few minutes, the reaction process is smooth and safe, products are easy to separate, and the preparation method accords with the development concept of green chemistry.
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Paragraph 0024
(2019/12/25)
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- Isolation and study of ruthenium–cobalt oxo cubanes bearing a high-valent, terminal RuV–Oxo with significant oxyl radical character
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High-valent RuV–oxo intermediates have long been proposed in catalytic oxidation chemistry, but investigations into their electronic and chemical properties have been limited due to their reactive nature and rarity. The incorporation of Ru into the [Co3O4] subcluster via the single-step assembly reaction of CoII(OAc)2(H2O)4 (OAc = acetate), perruthenate (RuO4 –), and pyridine (py) yielded an unprecedented Ru(O)Co3(μ3-O)4(OAc)4(py)3 cubane featuring an isolable, yet reactive, RuV–oxo moiety. EPR, ENDOR, and DFT studies reveal a valence-localized [RuV(S = 1/2)CoIII 3(S = 0)O4] configuration and non-negligible covalency in the cubane core. Significant oxyl radical character in the RuV–oxo unit is experimentally demonstrated by radical coupling reactions between the oxo cubane and both 2,4,6-tri-tert-butylphenoxyl and trityl radicals. The oxo cubane oxidizes organic substrates and, notably, reacts with water to form an isolable μ-oxo bis-cubane complex [(py)3(OAc)4Co3(μ3-O)4Ru]– O–[RuCo3(μ3-O)4(OAc)4(py)3]. Redox activity of the RuV–oxo fragment is easily tuned by the electron-donating ability of the distal pyridyl ligand set at the Co sites demonstrating strong electronic communication throughout the entire cubane cluster. Natural bond orbital calculations reveal cooperative orbital interactions of the [Co3O4] unit in supporting the RuV–oxo moiety via a strong π-electron donation.
- Amtawong, Jaruwan,Balcells, David,Wilcoxen, Jarett,Handford, Rex C.,Biggins, Naomi,Nguyen, Andy I.,David Britt,Don Tilley
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p. 9859 - 19869
(2019/12/25)
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